1. Field of the Invention
This invention relates to the method and apparatus for removing sulfur and nitrogen compounds from combustion gases before discharge to atmosphere. More particularly, the invention relates to absorbing sulfur dioxide and nitrogen oxides by a slurry of lime/limestone and catalyzing the reaction between the nitrogen oxides and sulfites and bisulfites with subsequent recovery of the catalyst and ammonia.
2. Description of the Prior Art
The Air Quality Control System (AQCS) has been primarily developed to remove SO.sub.2 from combustion gases. A slurry of water and lime/limestone is brought into physical contact with combustion gases to be scrubbed. Many techniques have been developed to implement the absorption of SO.sub.2 from flue gases with the lime/limestone slurry. Continual improvements are demanded in the art so as to overcome increasing costs.
A technical demand in the art is to remove oxides of nitrogen from combustion gases. There are limited means to control these compounds by temperature of the combustion process. There remain nitrogen oxides which could be removed at the same time the sulfur dioxide is scrubbed from the gases.